Blood test spots Alzheimer's before symptoms hit

A team of neurologists has developed a blood test that can identify with 90 percent
accuracy whether someone is likely to experience symptoms of
dementia in the preceding two to three years.

The test, if proven to be reliable, could mean trials attempting
to modify the disease before it takes hold could be carried out far
earlier on groups at risk.

As the team behind the study points out in a paper published in
Nature Medicine, our lack of any cure to date "may be due
to our inability to detect the disease before it has progressed to
produce evident memory loss and functional decline".

Currently the Alzheimer's tests in our repertoire do not give
anywhere near the kind of speed and ease of diagnosis that a blood
test potentially could. Genetic mutations, for instance, can be
identified but are rare. It's why one ongoing trial involving a Colombian
family of 5,000 with one of these hereditary mutations has been
so surprising and important to the field. Otherwise, it's possible
to identify amyloid beta plaques in the brain or a protein called
tau, both signs of the disease, in brain scans. However these
processes are costly and would only be carried out if a person were
already deemed at risk or in the early stages.

The Georgetown University Medical Centre team that carried out
the blood test study looked for biomarkers among 525 individuals
aged 70 and older across a five-year period, taking blood samples
annually. As the study progressed, 74 of these subjects developed
signs of mild Alzheimer's. Two to three years before those symptoms
developed, the team was able to identify "unambiguously" a set of
ten lipid metabolites in the blood plasma using mass spectrometry,
which predicted with 90 percent accuracy whether dementia would
occur.

"This biomarker panel, reflecting cell membrane integrity, may
be sensitive to early neurodegeneration of preclinical Alzheimer's
disease," the team hypothesised in the paper.

Professor of neurochemistry at Kings College London Paul
Francis, is cautiously optimistic at the news, calling the study a
"good indication that the blood study is worth pursuing".

"Anything which provides people that will develop dementia and
their families with an earlier sign of what's going to happen, with
a degree of certainty, is probably a good thing," Francis told
Wired.co.uk. "There are ethical issues of course about telling
people -- do people want to know? But the main reason is tell
people is so they have the longest time to prepare. They can make
their own decisions, because of course one of the things that
happens soon after a clinical diagnosis is people can't make their
own decisions. The empowerment to make your own decisions is a very
strong decision for going for early diagnosis."

In terms of treating the impending symptoms with those drugs we
already know to be somewhat effective, such as donepezil, Francis
says there is no evidence that providing them earlier would have
any effect. It is the chances of modifying the disease with
treatments beforehand, which could potentially benefit from an
earlier diagnosis, he says. "This could be an important stepping
stone for treatments that would actually hopefully put off the
disease or halt it."

One of the common markers for Alzheimer's are deposits of
amyloid beta in the brain, and this has become an area of focus for
treatment research. However it's thought that deposition begins 20
to 30 years prior to symptoms appearing. For this reason, Francis
suggests "it's possibly too late" to help if we identify the
disease two or three years prior. "The related clinical trials
already undertaken with vaccines and enzyme inhibitors have all
failed in their primary outcomes."

Nevertheless, that is not to say early diagnosis will not have
some benefit, he adds. "Until we've got the ability to predict with
90 percent accuracy who's going to develop dementia and who's not,
then we won't be able to do that study." This is exactly what the
blood test will help us achieve. It may simply help us realise that
intervention must be far earlier, perhaps even decades, to achieve
a cure.

"The point of doing this is to test the hypothesis, if we get in
there before they have symptoms, what effect would it have?"

"The first thing we need to know is does this blood test prove
true in a larger study -- then if we do a pilot study with these
types of amyloid beta approaches, do they in fact show benefit.
It's a steady step-by-step process."

Another area of research that could benefit, he suggests, is in
the targeting of the protein tau, common in Alzheimer's patients.
Changes to the protein occur closer to the time the symptoms
surface so could potentially pose a better target for anyone
diagnosed as being at risk two to three years beforehand.